1. Field of the Invention
The present invention relates to a fan, and more particularly to an adjustable and stable pre-loading device equipped fan.
2. Description of the Prior Art
As shown in FIG. 1(a), the conventional fan 10 includes a stator 20, at least one bearing 30, a rotor 50, a shaft 60 and a spring 70. The rotor 50 further includes a blade structure 55. Besides, the shaft 60 couples the rotor 50 to the bearing 30. As such, the shaft 60 enables the blade structure 55 of the rotor 50 to rotate. The shaft 60 passes through and compresses the spring 70, and then is coupled to the bearing 30. As such, the spring 70 applies a downward force, generally called pre-loading force, on the bearing 30.
Referring to FIG. 1(a) and FIG. 1(b), the bearing 30 is positioned on the bottom of the stator 20. In addition, the bearing 30 is composed of an inner ring 31, a plurality of balls 32 and an outer ring 33. The balls 32 couple the outer ring 33 to the outer periphery of the inner ring 31. During the inner ring 31 rotates respective to the outer ring 33, the balls 32 touch the inner ring 31 as well as the outer ring 33 and thus form the first contact 35 and the second contact 36, respectively. However, the prior art suffers from the problem that the pre-loading force is unstable. For example, the contacts may shift and the pre-loading force fails to be kept constant. The problem and the reason are described in detail as follows. The blade structure 55 may move vertically or horizontally due to some reasons, such as the flow disturbs the blade structure 55. In this case, the spring 70 maybe sometimes compressed and sometimes relaxed. As such, the spring 70 fails to apply constant pre-loading force on the bearing 30, and the first contact 35 and the second contact 36 do not stay at the same positions. As a result, the fan suffers form shake, noise and abrasion.
Besides, prior art fails to adjust the pre-loading force according to the requirement of the user since the spring 70 has been formed previously and thus has no adjustable elastic coefficient.
Accordingly, there has been a strongly felt need for a novel fan having stable pre-loading to solve the above-mentioned problem. Besides, it is desired that the applied pre-loading force is adjustable.
The present invention discloses an adjustable and stable pre-loading device equipped fan. That is, according to the present invention, the pre-loading applied on the bearing of the fan is adjustable. The present fan includes a stator, an elastic device, a first bearing, a second bearing, a first rigid spacer, a second rigid spacer, a rotor and a shaft. Among these, the stator includes a receptacle having the first threads formed thereon formed on the opposite ends.
The first rigid spacer is positioned in the receptacle. The first bearing is formed in the receptacle and further on the first rigid spacer. The elastic device is formed in the receptacle and further on the first bearing. The second bearing is formed in the receptacle and further on the elastic device. The second rigid spacer is formed in the receptacle and further on the second bearing. That is, the elastic device is directly compressed by and sandwiched between the first bearing and the second bearing. In addition, the elastic device is indirectly compressed by and sandwiched between the first rigid spacer and the second rigid spacer. In this manner, the first rigid spacer compresses the elastic device by means of the first bearing. Then, the elastic device applies pre-loading force on the first bearing due to the reactive force. Likewise, the second rigid spacer compresses the elastic device by means of the second bearing. Then, the elastic device applies pre-loading force on the second bearing due to the reactive force.
The rotor includes a blade structure. The shaft includes a first terminal, an opposite second terminal and a middle section interposed therebetween. Since the first terminal is coupled to the rotor, the shaft is able to rotate the blade structure of the rotor. Besides, the middle section sequentially passing through the first rigid spacer, the elastic device and the second rigid spacer is coupled to the inner rings of the first bearing and the second bearing.
The first bearing and the second bearing are composed of an inner ring, a plurality of balls and an outer ring, respectively. The balls couple the inner ring to the outer ring. During the inner ring rotates respective to the outer ring, the balls contact the inner ring and the outer ring, respectively.
The balls couple the inner ring to the outer ring. Therefore, there is a first contact formed between the inner ring and the ball. Besides, there is a second contact formed between the outer ring and the ball. Since the first rigid spacer and the opposite second rigid spacer isolate the blade structure from the elastic device, the blade structure which may vibrates does not affect the elastic device.
The pre-loading force applied by the elastic device on the first bearing and the second bearing is adjustable since the first rigid spacer and the second rigid spacer are coupled to the receptacle movably. For example, the user may alter the distance d between the first rigid spacer and the second rigid spacer to adjust the pre-loading force. Alternatively, the user alters the turns that the first thread meshes with the second thread to adjust the pre-loading force. The pre-loading force that the elastic device applies on the bearing is proportional to the turns.